1. Field of the Invention
This invention is broadly directed to an apparatus for washing mechanical parts carried by a tray or the like within an enclosure, and is more particularly directed to the drive mechanism for rotating the tray during the washing cycle.
2. Description of the Prior Art
Parts washing machines as described herein are designed to spray mechanical parts which are often large and heavy. The parts are typically covered with oil, grit or grease which must be removed before the mechanic can do further work. The parts are most often made of metal and may be damaged or may cause damage to a machine in which they are washed unless treated with care. On the other hand, parts washing machines must routinely handle loads in the range of 500 up to 4000 pounds, which requires great ruggedness throughout.
Many prior art machines have used solvents or the like to remove the grease and debris, but these solvents are increasingly disfavored for environmental reasons as they often pose hazardous wastes. As an alternative, machines which heat water and biodegradable detergents offer an advantage over the older style of machines.
In order to effectively clean the parts, they are often carried on baskets, shelves or trays so that spray nozzles can direct a cleaning fluid to remove the dirt and grime. In order to use effective and rugged spray apparatus, an enclosure is often provided and the tray on which the parts are mounted rotates to present different sides of the parts to the spray generated by the nozzles.
One problem which has been particularly vexing to those skilled in the art concerns the mechanism for driving the tray during rotation. Whether using rubber tires to frictionally engage the outer wall of the tray, or the use of a sprocket to drive a chain wrapped around the outer wall of the tray, these prior art mechanisms have proven to be prone to breakdown and excessive maintenance. The prior art drive mechanisms have heretofore required that the drive member be biased against the tray to maintain driving engagement. The biasing force, applied by springs or the like, exceeds forty pounds. Typically, the recommended transverse load on the bearings of the drive motors for the prior art machines has been about twelve pounds. As a result, premature bearing failure has been a constant problem in the prior art pans washing machines.